TITLE:   GCN CIRCULAR
NUMBER:  29408
SUBJECT: IPN triangulation of GRB 210204A
DATE:    21/02/05 23:27:45 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

K. Hurley, on behalf of the IPN,

I. G. Mitrofanov, D. V. Golovin, A. S. Kozyrev, M. L. Litvak,
and A. B. Sanin, on behalf of the HEND-Odyssey GRB team,

D. Svinkin, S. Golenetskii, D. Frederiks, A. Ridnaia,
A. Lysenko, and T. Cline on behalf of the Konus-Wind team,

A. Goldstein, M. S. Briggs, and C. Wilson-Hodge
on behalf of the Fermi GBM team,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,

S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT team, and

W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:

The long-duration GRB 210204A
(Fermi-GBM detection: The Fermi GBM team, GCN Circ. 29390;
Bissaldi, GCN Circ. 29393;
BALROG localization: Kunzweileret al., GCN Circ. 29391;
GECAM detection: Li, GCN Circ. 29392)
has been detected by Fermi (GBM trigger 634112970), INTEGRAL (SPI-ACS),
Konus-Wind, Mars-Odyssey (HEND), and Swift (BAT), so far,
at about 23365 s UT (06:29:25).
The burst was outside the coded field of view of the BAT.

We have triangulated it to a preliminary, error box
whose coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   118.116 (07h 52m 28s) +15.249 (+15d 14' 57")
  Corners:
   120.374 (08h 01m 30s) +23.758 (+23d 45' 30")
   115.277 (07h 41m 07s)  +4.395 ( +4d 23' 43")
   114.946 (07h 39m 47s)  +4.455 ( +4d 27' 16")
   120.017 (08h 00m 04s) +23.825 (+23d 49' 30")
  ---------------------------------------------
The error box area is 6.7 sq. deg, and its maximum
dimension is 20.0 deg (the minimum one is 20 arcmin).
The Sun distance was 155 deg.

This box may be improved.

The IPN localization is consistent with, but reduces the area of, the
Fermi RoboBA and BALROG localizations (GCN Circ. 29390 and 29391).

The optical transient ZTF21aagwbjr/AT2021buv (Kool et al., GCN Circ. 29405) 
is inside the box, lending support to the association of the transient and 
the burst.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB210204_T23570/IPN/

The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.